Secondary Air Injection System Relay B Circuit Malfunction
The P0419 code means the vehicle's onboard diagnostic system has detected: Secondary Air Injection System Relay B Circuit Malfunction. This is a low severity code.
- Keep driving?
- Yes, but fix soon
- DIY difficulty
- easy
- Estimated cost
- $30 - $200 (parts and labor)
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Common Symptoms
- Check Engine Light illuminated
- Secondary air pump on bank 2 does not activate
- No drivability issues
- Failed emissions test
Probable Causes (Ranked by Likelihood)
- Failed secondary air relay B Very High
- Open or shorted relay B control circuit High
- Corroded relay B socket Moderate
- ECM relay B driver circuit fault Low
Step-by-Step Diagnostic Procedure
-
Locate relay B in the fuse box and swap with a known-good relay
-
Check for power and ground at the relay B socket
-
Verify ECM commands relay B on during cold start with a scan tool
-
Inspect relay socket for corrosion or thermal damage
-
Check relay control wiring from ECM to relay B socket for continuity
Common Fixes by Vehicle
What techs usually find when diagnosing P0419 on specific vehicles — tap your vehicle for the fix and the exact part:
2007-2014 Subaru Tribeca/Outback 3.0L/3.6L H6 easy DIY
P0419 is the secondary air relay 'B' circuit (some Subaru H6 engines have two relays for bank-specific air injection). Replace the #2 SAI relay in the underhood fuse box. If the code persists after relay replacement, check the wiring between the PCM and the relay -- rodent damage in the passenger-side harness is common on these.
Labor: 20 min2006-2013 BMW X5/X6 4.8L N62 moderate DIY
N62 V8 has two secondary air pumps and two relays. P0419 points to bank 2's relay. Both relays are in the E-box. Replace in pairs because they age together. Also inspect the check valves at the head -- carbon fouling from failed check valves will set P0491/P0492 alongside P0419.
Labor: 45 min2005-2010 Audi Q7/A8 4.2L V8 moderate DIY
Audi 4.2L V8 has dual SAI relays. P0419 = bank 2 relay circuit fault. Relay J299 or J545 depending on year is under the dash near the driver's knee panel or in the E-box. Use VCDS to actuate the relay and check for the buzz of the pump. No buzz = relay or wiring, not pump.
Labor: 30-60 minFrequently Asked Questions
Can I drive with code P0419?
Yes. Relay B controls the air pump for bank 2 during cold starts only. No drivability impact during normal driving.
Why does my vehicle have two air pump relays?
V6 and V8 engines often use separate relays for each exhaust bank. This allows independent control of secondary air injection to each catalytic converter.
Can I replace relay B myself?
Yes. The relay is typically a plug-in component in the engine bay fuse box. No tools are required beyond locating the correct relay position using your owners manual or fuse box diagram.
Sources
This page is built from documented references. Verify against your own service info before repair work.
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